Crystal structure and solvent-dependent behaviours of 3-amino-1,6-diethyl-2,5,7-trimethyl-4,4-di-phenyl-3a,4a-di-aza-4-bora-s-indacene.

In the title compound (3-amino-4,4-diphenyl-BODIPY), C28H32BN3, the central six-membered ring has a flattened sofa conformation, with one of the N atoms deviating by 0.142 (4) Å from the mean plane of the other five atoms, which have an r.m.s. deviation of 0.015 Å. The dihedral angle between the two essentially planar outer five-membered rings is 8.0 (2)°. In the crystal, mol-ecules are linked via weak N-H⋯π inter-actions, forming chains along [010]. The com-pound displays solvent-dependent behaviours in both NMR and fluorescence spectroscopy. In the (1)H NMR spectra, the aliphatic resonance signals virtually coalesce in solvents such as chloro-form, di-chloro-methane and di-bromo-ethane; however, they are fully resolved in solvents such as dimethyl sulfoxide (DMSO), methanol and toluene. The excitation and fluorescence intensities in chloro-form decreased significantly over time, while in DMSO the decrease is not so profound. In toluene, the excitation and fluorescent intensities are not time-dependent. This behaviour is presumably attributed to the assembly of 3-amino-4,4-diphenyl-BODIPY in solution that leads to the formation of noncovalent structures, while in polar or aromatic solvents, the formation of these assemblies is disrupted, leading to resolution of signals in the NMR spectra.